Imaging device and digital camera using the imaging device

ABSTRACT

An imaging device has a zoom lens system having a plurality of lens units and forming an optical image of an object so as to continuously optically zoom by varying distances between the lens unit; and an image sensor converting the optical image formed by the zoom lens system to an electric signal. The zoom lens system has from an object side: a first lens unit being overall negative and including a reflecting surface that bends a luminous flux substantially 90 degrees; and a second lens unit disposed with a variable air distance from the first lens unit, and having a negative optical power.

RELATED APPLICATION

This application is based on application No. 2002-196171 filed in Japanon Jul. 4, 2002, the content of which is hereby incorporated byreference.

Field of the Invention

The present invention relates to an imaging device having an imagesensor that converts, to electric signals, optical images formed on thelight receiving surface of a charge coupled device (CCD), acomplementary metal-oxide semiconductor (CMOS) sensor or the like, andmore particularly, to an imaging device which is a principal element ofcameras incorporated in or externally attached to digital cameras,personal computers, mobile computers, mobile telephones, personaldigital assistances (PDAs) and the like. Specifically, the presentinvention relates to a compact imaging device having a zoom lens system.

Description of the Prior Art

In recent years, digital cameras have been rapidly becoming widespreadthat convert an optical image to electronic signals by using an imagesensor such as a CCD or a CMOS sensor instead of silver halide film,convert the data to digital form, and record or transfer the digitizeddata. In such digital cameras, since CCDs and CMOS sensors having highpixels such as two million pixels and three million pixels arecomparatively inexpensively provided recently, a high-performanceimaging device mounted with an image sensor is in greatly increasingdemand. In particular, a compact imaging device is desired that isprovided with a zoom lens system capable of performing zooming withoutany image quality degradation.

Further, in recent years, imaging devices have been becomingincorporated in or externally attached to personal computers, mobilecomputers, mobile telephones, PDAs and the like because of improvementsin the image processing capability of semiconductor elements and thelike, which spurs the demand for a high-performance imaging device.

As zoom lens systems used for such imaging devices, so-called minus leadzoom lens systems in which the lens unit disposed on the most objectside has a negative optical power are proposed in large numbers. Minuslead zoom lens systems have features such that they are easily madewide-angle and that the lens back focal length necessary for insertingan optical low-pass filter is easily secured.

Conventional examples of minus lead zoom lens systems include zoom lenssystems proposed as taking lens systems for film-based cameras. However,in these zoom lens systems, since the exit pupil of the lens system inthe shortest focal length condition is situated comparatively near theimage plane, it does not match with the pupil of the microlens providedso as to correspond to each pixel of the image sensor having highpixels, so that a sufficient quantity of peripheral light cannot besecured. In addition, since the position of the exit pupil largelyvaries during zooming, the setting of the pupil of the microlens isdifficult. Further, since required optical performance such as spatialfrequency characteristics is completely different between silver halidefilm and image sensors to begin with, optical performance required ofimage sensors cannot be sufficiently secured. For these reasons, therehas emerged a need for the development of a dedicated zoom lens systemoptimized for imaging devices having an image sensor.

On the other hand, to reduce the size of the imaging device, a proposalhas been made to attain size reduction without any change in opticalpath length by bending the zoom lens system in the middle of the opticalpath. For example, Japanese Laid-Open Patent Application No. H11-196303proposes an imaging device where in a minus lead zoom lens system, areflecting surface is provided on the optical path and the optical pathis bent substantially 90 degrees by the reflecting surface and thenforms an optical image on the image sensor by way of movable lens units.The imaging device disclosed by this application has a structure that areflecting surface is provided on the image side of a fixed lens elementof a negative meniscus configuration and the optical path is bentsubstantially 90 degrees by the reflecting surface and then reaches theimage sensor by way of two movable positive lens units and a fixedpositive lens unit.

As another example, Japanese Laid-Open Patent Application No. H11-258678discloses a structure that a reflecting surface is provided on the imageside of a fixed lens element of a negative meniscus configuration and amovable positive lens unit and the optical path is bent substantially 90degrees by the reflecting surface and then reaches the image sensor byway of a positive lens unit.

However, in these two applications, only the lens barrel structure isdisclosed and no specific zoom lens system structure is shown. It isdifficult to reduce the overall size of imaging devices having a zoomlens system unless the zoom lens system taking up the largest space involume is optimized.

OBJECT AND SUMMARY

An object of the present invention is to provide an improved imagingdevice.

Another object of the present invention is to provide an imaging devicebeing compact although having a high-performance and high-magnificationzoom lens system.

The above-mentioned objects are attained by an imaging device having thefollowing structure:

An imaging device comprising: a zoom lens system having a plurality oflens units and forming an optical image of an object so as tocontinuously optically zoom by varying distances between the lens unit;and an image sensor converting the optical image formed by the zoom lenssystem to an electric signal, wherein the zoom lens system comprisesfrom an object side: a first lens unit being overall negative andincluding a reflecting surface that bends a luminous flux substantially90 degrees; and a second lens unit disposed with a variable air distancefrom the first lens unit, and having a negative optical power.

Moreover, another aspect of the present invention is a digital cameraincluding the above-described imaging device. While the term digitalcamera conventionally denotes cameras that record only optical stillimages, cameras that can handle moving images as well and home digitalvideo cameras have also been proposed and at present, there is nodistinction between cameras that record only still images and camerasthat can handle moving images as well. Therefore, in the followingdescription, the term digital camera includes all of the cameras such asdigital still cameras and digital movie cameras where an imaging devicehaving an image sensor that converts optical images formed on the lightreceiving surface of the image sensor to electric signals is a principalelement.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of this invention will become clearfrom the following description, taken in conjunction with the preferredembodiments with reference to the accompanied drawings in which:

FIG. 1 is a lens construction view of a first embodiment (firstexample);

FIG. 2 is a lens construction view of a second embodiment (secondexample);

FIG. 3 is a lens construction view of a third embodiment (thirdexample);

FIG. 4 is a lens construction view of a fourth embodiment (fourthexample);

FIG. 5 is a lens construction view of a fifth embodiment (fifthexample);

FIG. 6 is a lens construction view of a sixth embodiment (sixthexample);

FIG. 7 is a lens construction view of a seventh embodiment (seventhexample);

FIG. 8 is a lens construction view of an eighth embodiment (eighthexample);

FIG. 9 is a lens construction view of a ninth embodiment (ninthexample);

FIG. 10 is a lens construction view of a tenth embodiment (tenthexample);

FIGS. 11A to 11I are graphic representations of aberrations of the firstembodiment in in-focus state at infinity;

FIGS. 12A to 12I are graphic representations of aberrations of thesecond embodiment in in-focus state at infinity;

FIGS. 13A to 13I are graphic representations of aberrations of the thirdembodiment in in-focus state at infinity;

FIGS. 14A to 14I are graphic representations of aberrations of thefourth embodiment in in-focus state at infinity;

FIGS. 15A to 15I are graphic representations of aberrations of the fifthembodiment in in-focus state at infinity;

FIGS. 16A to 16I are graphic representations of aberrations of the sixthembodiment in in-focus state at infinity;

FIGS. 17A to 17I are graphic representations of aberrations of theseventh embodiment in in-focus state at infinity;

FIGS. 18A to 18I are graphic representations of aberrations of theeighth embodiment in in-focus state at infinity;

FIGS. 19A to 19I are graphic representations of aberrations of the ninthembodiment in in-focus state at infinity;

FIGS. 20A to 20I are graphic representations of aberrations of the tenthembodiment in in-focus state at infinity;

FIG. 21 is a construction view showing the present invention in outline;and

FIG. 22 is a construction view showing the use condition of the presentinvention in the shortest focal length condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, an embodiment of the present invention willbe described.

An imaging device according to the embodiment of the present inventioncomprises, for example as shown in FIG. 21, from the object side(subject side): a zoom lens system TL forming an optical image of anobject so as to zoom, an optical low-pass filter LPF, and an imagesensor SR converting the optical image formed by the zoom lens system TLto electric signals. The zoom lens system comprises a first lens unitGr1 including a prism PR having a reflecting surface inside, andsucceeding lens units. The imaging device is a principal element ofcameras incorporated in or externally attached to digital cameras, videocameras, personal computers, mobile computers, mobile telephones, PDAsand the like.

The zoom lens system TL comprises a plurality of lens units includingthe first lens unit Gr1. The size of the optical image can be varied byvarying the distances between the lens units. The first lens unit Gr1has a negative optical power, and includes the prism PR that bends theoptical axis of the object light substantially 90 degrees.

The optical low-pass filter LPF has a specific cutoff frequency foradjusting the spatial frequency characteristics of the taking lenssystem to thereby eliminate the color moire generated in the imagesensor. The optical low-pass filter of the embodiment is a birefringentlow-pass filter formed by laminating a birefringent material such ascrystal having its crystallographic axis adjusted in a predetermineddirection, wave plates changing the plane of polarization, or the like.As the optical low-pass filter, a phase low-pass filter or the like maybe adopted that attains necessary optical cutoff frequencycharacteristics by a diffraction effect.

The image sensor SR comprises a CCD having a plurality of pixels, andconverts the optical image formed by the zoom lens system to electricsignals by the CCD. The signals generated by the image sensor SR undergopredetermined digital image processing or image compression processingas required, and are recorded into a memory (a semiconductor memory, anoptical disk, etc.) as digital video signals or in some cases,transferred to another apparatus through a cable or by being convertedto infrared signals. A CMOS sensor may be used instead of a CCD.

FIGS. 1 to 10 are construction views showing the lens arrangements, inthe shortest focal length condition, of the zoom lens systems includedin imaging devices according to a first to a tenth embodiment of thepresent invention. In these figures, the prism PR having an internalreflection surface is illustrated as a plane-parallel plate, and theoptical path is illustrated as a straight line.

A zoom lens system of the first embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element convex to the objectside, and a plate PR corresponding to the prism; a second lens unit Gr2including a second lens element L2 of a bi-concave configuration and athird lens element L3 of a positive meniscus configuration convex to theobject side; a diaphragm ST; a third lens unit Gr3 including a firstdoublet lens element DL1 consisting of a fourth lens element L4 of abi-convex configuration and a fifth lens element L5 of a bi-concaveconfiguration; a fourth lens unit Gr4 including a sixth lens element L6of a positive meniscus configuration concave to the object side; and afifth lens unit Gr5 including a seventh lens element L7 of a negativemeniscus configuration concave to the object side. On the image side ofthe fifth lens unit Gr5 of this zoom lens system, a plane-parallel plateLPF corresponding to the optical low-pass filter is disposed. In thisembodiment, the first lens unit Gr1 and the second lens unit Gr2 have anegative optical power, the third lens unit Gr3 and the fourth lens unitGr4 have a positive optical power, and the fifth lens unit Gr5 has anegative optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the fifth lens unit Gr5 isfixed with respect to the image plane with the plane-parallel plate LPFdisposed on the image side of the fifth lens unit Gr5.

Of the surfaces of the lens elements, both side surfaces of the secondlens element L2, the image side surface of the sixth lens element L6 andthe object side surface of the seventh lens element L7 are aspherical.

FIG. 22 is a construction view showing the use condition, in theshortest focal length condition, of the zoom lens system of the firstembodiment. As mentioned above, the optical axis of the first lenselement L1 being a negative meniscus lens element convex to the objectside, or the optical axis OAX of the object light, and the optical axisof the prism PR, or the optical axis IAX of the image light, form anangle of 90 degrees. With this construction, an imaging device beingextremely thin in the direction of the optical axis OAX of the objectside can be structured.

A zoom lens system of the second embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element convex to the objectside, a plate PR corresponding to the prism, and a second lens elementL2 of a positive meniscus configuration convex to the object side; asecond lens unit Gr2 including a third lens element L3 of a negativemeniscus configuration convex to the object side and a fourth lenselement L4 of a positive meniscus configuration convex to the objectside; a diaphragm ST; a third lens unit Gr3 including a first doubletlens element DL1 consisting of a fifth lens element L5 of a bi-convexconfiguration and a sixth lens element L6 of a bi-concave configuration;a fourth lens unit Gr4 including a seventh lens element L7 of a positivemeniscus configuration concave to the object side; and a fifth lens unitGr5 including an eighth lens element L8 of a negative meniscusconfiguration convex to the object side. On the image side of the fifthlens unit Gr5 of this zoom lens system, a plane-parallel plate LPFcorresponding to the optical low-pass filter is disposed. In thisembodiment, the first lens unit Gr1 and the second lens unit Gr2 have anegative optical power, the third lens unit Gr3 and the fourth lens unitGr4 have a positive optical power, and the fifth lens unit Gr5 has anegative optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the fifth lens unit Gr5 isfixed with respect to the image plane together with the plane-parallelplate LPF disposed on the image side of the fifth lens unit Gr5.

Of the surfaces of the lens elements, the object side surface of thefirst lens element L1, both side surfaces of the third lens element L3,the image side surface of the seventh lens element L7 and the objectside surface of the eighth lens element are aspherical.

A zoom lens system of the third embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element convex to the objectside, and a plate PR corresponding to the prism; a second lens unit Gr2including a second lens element L2 of a negative meniscus configurationconvex to the object side and a third lens element L3 of a positivemeniscus configuration convex to the object side; a diaphragm ST; athird lens unit Gr3 including a first doublet lens element DL1consisting of a fourth lens element L4 of a bi-convex configuration anda fifth lens element L5 of a bi-concave configuration; a fourth lensunit Gr4 including a sixth lens element L6 of a positive meniscusconfiguration concave to the object side; and a fifth lens unit Gr5including a seventh lens element L7 of a negative meniscus configurationconvex to the object side. On the image side of the fifth lens unit Gr5of this zoom lens system, a plane-parallel plate LPF corresponding tothe optical low-pass filter is disposed. In this embodiment, the firstlens unit Gr1 and the second lens unit Gr2 have a negative opticalpower, the third lens unit Gr3 and the fourth lens unit Gr4 have apositive optical power, and the fifth lens unit Gr5 has a negativeoptical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the fifth lens unit Gr5 isfixed with respect to the image plane together with the plane-parallelplate LPF disposed on the image side of the fifth lens unit Gr5.

Of the surfaces of the lens elements, both side surfaces of the secondlens element L2, the image side surface of the fifth lens element L5 andboth side surfaces of the sixth lens element L6 are aspherical.

A zoom lens system of the fourth embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element convex to the objectside, and a plane PR corresponding to the prism; a second lens unit Gr2including a second lens element L2 of a negative meniscus configurationconvex to the object side and a third lens element L3 of a positivemeniscus configuration convex to the object side; a diaphragm St; athird lens unit Gr3 including a fourth lens element L4 of a bi-convexconfiguration and a first doublet lens element DL1 consisting of a fifthlens element L5 of a positive meniscus configuration concave to theobject side and a sixth lens element L6 of a negative meniscusconfiguration concave to the object side; and a fourth lens unit Gr4including a seventh lens element L7 of a bi-convex configuration. On theimage side of the fourth lens unit Gr4 of this zoom lens system, aplane-parallel plate LPF corresponding to the optical low-pass filter isdisposed. In this embodiment, the first lens unit Gr1 and the secondlens unit Gr2 have a negative optical power, and the third lens unit Gr3and the fourth lens unit Gr4 have a positive optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the plane-parallel plateLPF is fixed with respect to the image plane.

Of the surfaces of the lens elements, both side surfaces of the secondlens element L2, the image side surface of the sixth lens element L6 andthe both side surfaces of the seventh lens element L7 are aspherical.

A zoom lens system of the fifth embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element concave to the objectside, and a plate PR corresponding to the prism; a second lens unit Gr2including a second lens element L2 of a negative meniscus configurationconvex to the object side and a third lens element L3 of a positivemeniscus configuration convex to the object side; a diaphragm ST; athird lens unit Gr3 including a first doublet lens element DL1consisting of a fourth lens element L4 of a bi-convex configuration anda fifth lens element L5 of a bi-concave configuration; and a fourth lensunit Gr4 including a sixth lens element L6 of a positive meniscusconfiguration convex to the object side. On the image side of the fourthlens unit Gr4 of this zoom lens system, a plane-parallel plate LPFcorresponding to the optical low-pass filter is disposed. In thisembodiment, the first lens unit Gr1 and the second lens unit Gr2 have anegative optical power, and the third lens unit Gr3 and the fourth lensunit Gr4 have a positive optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the plane-parallel plateLPF is fixed with respect to the image plane.

Of the surfaces of the lens elements, both side surfaces of the secondlens element L2, the image side surface of the fifth lens element L5 andthe both side surfaces of the sixth lens element L6 are aspherical.

A zoom lens system of the sixth embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element convex to the objectside, and a plate PR corresponding to the prism; a second lens unit Gr2including a second lens element L2 of a negative meniscus configurationconvex to the object side and a third lens element L3 of a positivemeniscus configuration convex to the object side; a diaphragm ST; athird lens unit Gr3 including a first doublet lens element DL1consisting of a fourth lens element L4 of a bi-convex configuration anda fifth lens element L5 of a bi-concave configuration; and a fourth lensunit Gr4 including a sixth lens element L6 of a negative meniscusconfiguration concave to the object side. On the image side of thefourth lens unit Gr4 of this zoom lens system, a plane-parallel plateLPF corresponding to the optical low-pass filter is disposed. In thisembodiment, the first lens unit Gr1 and the second lens unit Gr2 have anegative optical power, and the third lens unit Gr3 and the fourth lensunit Gr4 have a positive optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the plane-parallel plateLPF is fixed with respect to the image plane.

Of the surfaces of the lens elements, both side surfaces of the secondlens element L2, the image side surface of the fifth lens element L5 andthe both side surfaces of the sixth lens element L6 are aspherical.

A zoom lens system of the seventh embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a fist lenselement L1 being a negative meniscus lens element convex to the objectside, a second lens element L2 of a positive meniscus configurationconvex to the object side, and a plane PR corresponding to the prism; asecond lens unit Gr2 including a third lens element L3 of a negativemeniscus configuration convex to the object side and a fourth lenselement L4 of a positive meniscus configuration convex to the objectside; a diaphragm ST; a third lens unit Gr3 including a first doubletlens element DL1 consisting of a fifth lens element L5 of a bi-convexconfiguration and a sixth lens element L6 of a bi-concave configuration;and a fourth lens unit Gr4 including a seventh lens element L7 of anegative meniscus configuration concave to the object side. On the imageside of the fourth lens unit Gr4 of this zoom lens system, aplane-parallel plate LPF corresponding to the optical low-pass filter isdisposed. In this embodiment, the first lens unit Gr1 and the secondlens unit Gr2 have a negative optical power, and the third lens unit Gr3and the fourth lens unit Gr4 have a positive optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the plane-parallel plateLPF is fixed with respect to the image plane.

Of the surfaces of the lens elements, the image side surface of thethird lens element L3, the image side surface of the fourth lens elementL4, the image side surface of the sixth lens element L6 and both sidesurfaces of the seventh lens element L7 are aspherical.

A zoom lens system of the eighth embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element convex to the objectside and a plane PR corresponding to the prism; a second lens unit Gr2including a second lens element L2 of a bi-concave configuration and athird lens element L3 of a positive meniscus configuration convex to theobject side; a diaphragm ST; a third lens unit Gr3 including a firstdoublet lens element DL1 consisting of a fourth lens element L4 of abi-convex configuration and a fifth lens element L5 of a bi-concaveconfiguration, and a sixth lens element L6 of a negative meniscusconfiguration convex to the object side; and a fourth lens unit Gr4including a seventh lens element L7 of a negative meniscus configurationconcave to the object side. On the image side of the fourth lens unitGr4 of this zoom lens system, a plane-parallel plate LPF correspondingto the optical low-pass filter is disposed. In this embodiment, thefirst lens unit Gr1 and the second lens unit Gr2 have a negative opticalpower, and the third lens unit Gr3 and the fourth lens unit Gr4 have apositive optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the plane-parallel plateLPF is fixed with respect to the image plane.

Of the surfaces of the lens elements, the image side surface of thesecond lens element L2, the image side surface of the third lenselement, the image side surface of the sixth lens element L6 and bothside surfaces of the seventh lens element L7 are aspherical.

A zoom lens system of the ninth embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element convex to the objectside, a second lens element L2 of a positive meniscus configurationconvex to the object side, and a plane PR corresponding to the prism; asecond lens unit Gr2 including a third lens element L3 of a bi-concaveconfiguration and a fourth lens element L4 of a positive meniscusconfiguration convex to the object side; a diaphragm ST; a third lensunit Gr3 including a first doublet lens element DL1 consisting of afifth lens element L5 of a bi-convex configuration and a sixth lenselement L6 of a bi-concave configuration; and a fourth lens unit Gr4including a seventh lens element L7 of a positive meniscus configurationconcave to the object side. On the image side of the fourth lens unitGr4 of this zoom lens system, a plane-parallel plate LPF correspondingto the optical low-pass filter is disposed. In this embodiment, thefirst lens unit Gr1 and the second lens unit Gr2 have a negative opticalpower, and the third lens unit Gr3 and the fourth lens unit Gr4 have apositive optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the plane-parallel plateLPF is fixed with respect to the image plane.

Of the lens surfaces, the object side surface of the second lens elementL2, the image side surface of the third lens element L3, the image sidesurface of the fourth lens element L4, the image side surface of thesixth lens element L6 and both side surfaces of the seventh lens elementL7 are aspherical.

A zoom lens system of the tenth embodiment comprises from the objectside to the image side: a first lens unit Gr1 including a first lenselement L1 being a negative meniscus lens element convex to the objectside, and a plane PR corresponding to the prism; a second lens unit Gr2including a second lens element L2 of a bi-concave configuration and athird lens element L3 of a positive meniscus configuration convex to theobject side; a diaphragm ST; a third lens unit Gr3 including a firstdoublet lens element DL1 consisting of a fourth lens element L4 of abi-convex configuration and a fifth lens element L5 of a bi-concaveconfiguration; a fourth lens unit Gr4 including a sixth lens element L6of a negative meniscus configuration concave to the object side; and afifth lens unit Gr5 including a seventh lens element L7 of a bi-concaveconfiguration. On the image side of the fifth lens unit Gr5 of this zoomlens system, a plane-parallel plate LPF corresponding to the opticallow-pass filter is disposed. In this embodiment, the first lens unit Gr1and the second lens unit Gr2 have a negative optical power, the thirdlens unit Gr3 and the fourth lens unit Gr4 have a positive opticalpower, and the fifth lens unit Gr5 has a negative optical power.

In this zoom lens system, in zooming from the shortest focal lengthcondition to the longest focal length condition, the first lens unit Gr1is fixed with respect to the image plane, the second lens unit Gr2 movesso as to draw a locus of a U-turn convex to the image side such that itfirst moves toward the image side and then moves toward the object side,the third lens unit Gr3 substantially monotonously moves toward theobject side integrally with the diaphragm ST disposed on the object sideof the third lens unit Gr3, the fourth lens unit Gr4 substantiallymonotonously moves toward the image side, and the fifth lens unit Gr5 isfixed with respect to the image plane together with the plane-parallelplate LPF disposed on the image side of the fifth lens unit Gr5.

Of the surfaces of the lens elements, the image side surface of thethird lens element L3, the image side surface of the fourth lens elementL4, the image side surface of the sixth lens element L6 and both sidesurfaces of the seventh lens element L7 are aspherical.

In the zoom lens systems of these embodiments, the prism PR having areflecting surface that bends the optical axis of the object lightsubstantially 90 degrees is provided in the first lens unit. By thusbending the optical axis of the object light substantially 90 degrees,the apparent thickness of the imaging device can be reduced.

When a digital camera is taken as an example, the element that takes upthe largest volume in the apparatus is the imaging device including thezoom lens system. Particularly, when in digital cameras, opticalelements such as lens elements and a diaphragm included in the zoom lenssystem are arranged in line without the direction of the optical axisbeing changed like in conventional lens-shutter type film-based cameras,the size of the camera in the direction of the thickness substantiallydepends on the distance from the most object side element of the zoomlens system to the image sensor included in the imaging device. However,the aberration correction level of imaging devices have dramaticallyimproved with the increase in the number of pixels of image sensors inrecent years. Consequently, the number of lens elements of the zoom lenssystems included in imaging devices never stop increasing, so thatbecause of the thickness of the lens elements, it is difficult to reducethe thickness even when the camera is not used (in so-called collapsedcondition).

On the contrary, by adopting the structure that the optical axis of theobject light is bent substantially 90 degrees by the reflecting surfacelike the zoom lens systems of the embodiments, the size of the imagingdevice in the direction of the thickness can be reduced to the distancefrom the most object side lens element to the reflecting surface whenthe camera is not used, so that the apparent thickness of the imagingdevice can be reduced. Moreover, by adopting the structure that theoptical axis of the object light substantially 90 degrees by thereflecting surface, the optical path of the object light can be foldedin the vicinity of the reflecting surface, so that space can beeffectively used and further size reduction of the imaging device can beattained.

It is desirable that the reflecting surface be disposed in the firstlens unit Gr1. By disposing the reflecting surface in the first lensunit Gr1 disposed on the most object side, the size of the imagingdevice in the direction of the thickness can be minimized.

It is desirable that the first lens unit Gr1 including the reflectingsurface have a negative optical power. By the first lens unit Gr1 havinga negative optical power, the size of the reflecting surface in thereflecting surface position can be reduced. Moreover, by adopting thestructure that the first lens unit Gr1 has a negative optical power, thezoom lens system is of a so-called minus lead type. Minus lead type zoomlens systems are desirable because it is easy for them to adopt aretrofocus type structure in a wide focal length range and attain theimage-side telecentricity necessary for optical systems for formingoptical images on the image sensor.

While any of (a) an internal reflection prism (embodiments), (b) asurface reflection prism, (c) an internal reflection plane mirror and(d) a surface reflection mirror may be adopted as the reflectingsurface, (a) an internal reflection mirror is the most suitable. Byadopting an internal reflection prism, the object light passes throughthe medium of the prism, so that the axial distance when the objectlight passes through the prism is a reduced axial distance shorter thanthe normal air distance in accordance with the refractive index of themedium. For this reason, it is desirable that an internal reflectionprism be adopted as the structure of the reflecting surface because anoptically equivalent structure can be attained with a smaller space.

When the reflecting surface is an internal reflection prism, it isdesirable that the material of the prism satisfy the followingcondition:Np≧1.55  (1)where Np is the refractive index of the material of the prism.

When the refractive index of the prism be lower than this range, thecontribution to size reduction is small. Therefore, it is undesirablethat the refractive index of the prism be lower than this range.

In addition to this range, it is desirable that the refractive index bewithin the following range:Np≧1.7  (1)′

The reflecting surface is not necessarily a complete total reflectionsurface. The reflectance of part of the reflecting surface may beappropriately adjusted so that part of the object light branches off soas to be incident on a sensor for metering or distance measurement.Moreover, the reflectance of the entire area of the reflecting surfacemay be appropriately adjusted so that the finder light branches. Whilethe incident surface and the exit surface of the prism are both plane inthe embodiments, they may have an optical power.

It is desirable that not more than two lens elements be disposed on theobject side of the reflecting surface. In a structure having in thefirst lens unit the prism PR having a reflecting surface that bends theoptical axis of the object light substantially 90 degrees, the thicknessof the optical system substantially depends on the distance from theobject side surface of the lens element disposed on the most object sideto the reflecting surface. Therefore, by disposing not more than twolens elements on the object side of the reflecting surface, a thinoptical system can be obtained. In particular, when the first lens unitGr1 includes only one lens element and the reflecting surface, thedegree of freedom of the lens barrel structure can be increased, so thatcost reduction of the imaging device can be attained. When the firstlens unit Gr1 includes only two lens elements and the reflectingsurface, relative decentration aberration correction can be performed,which is advantageous in optical performance.

Further, it is desirable that the first lens unit Gr1 be fixed withrespect to the image plane during zooming. Since the first lens unit Gr1includes the reflecting surface, moving it requires a large space, andin particular, when the reflecting surface comprises a prism, it isnecessary to move a prism having a large weight, so that a heavy burdenis placed on the driving mechanism. Moreover, by the first lens unit Gr1being fixed with respect to the image plane during zooming, an opticalsystem whose overall length does not vary can be obtained. Moreover,since the lens barrel structure can be simplified, cost reduction of theimaging device can be attained. Further, by adopting the structure thatthe first lens unit Gr1 is fixed during zooming, particularly in digitalcameras, it is easy to initialize the control system for controlling thelens units movable during zooming, so that the time necessary for thecamera to become ready to photograph when the main power is turned oncan be reduced.

The zoom lens systems of the embodiments adopt a structure that thesecond lens unit Gr2 succeeding the first lens unit Gr1 having anegative optical power also has a negative optical power. This structureis desirable because it makes it easy to adopt the above-mentionedstructure that the first lens unit Gr1 is fixed.

Next, conditions desirably satisfied by the embodiments will bedescribed. It is to be noted that while the corresponding effect can beattained by satisfying any one of the conditions alone, it is moredesirable that a plurality of conditions be satisfied from the viewpointof optical performance and size reduction.

It is desirable that the zoom lens systems of the embodiments satisfythe following condition0.5<|f1/f2|<5  (2)where f1 is the focal length of the first lens unit Gr1 and f2 is thefocal length of the second lens unit Gr2.

The condition (2) defines the desirable ratio between the focal lengthsof the first lens unit Gr1 and the second lens unit Gr2. When the lowerlimit of the condition (2) is exceeded, since the focal length of thefirst lens unit Gr1 is too short, distortion (particularly the negativedistortion in the shortest focal length condition) is extraordinary, sothat it is difficult to secure excellent optical performance. When theupper limit of the condition (2) is exceeded, since the focal length ofthe first lens unit Gr1 is too long, the negative optical power of thefirst lens unit Gr1 is weak, so that the diameter of the first lens unitGr1 increases, which is undesirable in view of size reduction.

Further, it is desirable that the zoom lens systems of the embodimentssatisfy the following condition:1.5<|f12w|/fw<4  (3)where f12w is the composite focal length of the first lens unit Gr1 andthe second lens unit Gr2 in the shortest focal length condition and fwis the overall focal length of the lens system in the shortest focallength condition.

The condition (3) relates to the composite focal length of the firstlens unit Gr1 and the second lens unit Gr2 in the shortest focal lengthcondition. When the upper limit of the condition (3) is exceeded, theoverall length increases because the composite focal length of the firstlens unit Gr1 and the second lens unit Gr2 is too long, and the lensdiameter increases because the composite optical power of the first lensunit Gr1 and the second lens unit Gr2 is weak. Consequently, it isdifficult to obtain a compact zoom lens system. When the lower limit ofthe condition (3) is exceeded, since the composite focal length of thefirst lens unit Gr1 and the second lens unit Gr2 is too short, thenegative distortion generated in the first lens unit Gr1 and the secondlens unit Gr2 is too large and difficult to correct in the shortestfocal length condition.

Further, it is desirable that the zoom lens systems of the embodimentssatisfy the following condition:0.4<|f12w|/f3<1.5  (4)where f12w is the composite focal length of the first lens unit Gr1 andthe second lens unit Gr2 in the shortest focal length condition and f3is the focal length of the third lens unit Gr3.

The condition (4) relates to the ratio between the composite focallength of the first lens unit Gr1 and the second lens unit Gr2 and thefocal length of the third lens unit Gr3 in the shortest focal length.That the upper limit of the condition (4) is exceeded means that thecomposite focal length of the first lens unit Gr1 and the second lensunit Gr2 is relatively long. Therefore, it is undesirable that the upperlimit of the condition (4) be exceeded because the position of the exitpupil shifts toward the image side. When the lower limit of thecondition (4) is exceeded, since the composite focal length of the firstlens unit Gr1 and the second lens unit Gr2 is too short, the negativedistortion generated in the first lens unit Gr1 and the second lens unitGr2 is too large and difficult to correct in the shortest focal lengthcondition.

It is preferable that zoom lens system satisfy the following condition(5):1.0<D/fw<2.6  (5)where D represents an axial distance between surface at the most objectside surface of the first lens unit and reflection surface; and fwrepresents a focal length of the entire zoom lens system in a wide anglecondition.

The condition (5) defines the preferable relation the axial distancebetween surface at the most object side surface of the first lens unitand reflection surface. This condition (5) is required to miniaturizethe entire optical system having reflection surface. If the lower limitof condition (5) were be transgressed, the optical power of the lenselements at the object side of the reflection surface would be toostrong. This would cause a distortion so large (especially the negativedistortion on the wide-angle end) that it would be impossible to securesatisfactory optical performance. By contrast, if the upper limit ofcondition (5) were to be transgressed, the axial distance betweensurface at the most object side surface of the first lens unit andreflection surface would be too long, which is undesirable in term ofminiaturization. In addition to the above-mentioned range, it ispreferable that the following range (5)′ is fulfilled:D/fw<2.2  (5)′

While the lens units of the embodiments comprise only refractive typelens elements that deflect the incident ray by refraction (that is, lenselements of a type in which the incident ray is deflected at theinterface between media having different refractive indices), thepresent invention is not limited thereto. For example, the lens unitsmay comprise diffractive type lens elements that deflect the incidentray by diffraction, refractive-diffractive hybrid lens elements thatdeflect the incident ray by a combination of diffraction and refraction,or gradient index lens elements that deflect the incident ray by thedistribution of refractive index in the medium.

The construction of the zoom lens systems included in the imaging deviceembodying the present invention will be more concretely described withreference to construction data, graphic representations of aberrationsand the like. A first to a tenth example described here as examplescorresponds to the first to the tenth embodiments described above. Thelens construction views (FIGS. 1 to 10) showing the first to the tenthembodiments show the lens arrangements of the corresponding first totenth examples.

In the construction data of the examples, ri (i=1,2,3, . . . ) is theradius (mm) of curvature of the i-th surface counted from the objectside, di (i=1,2,3, . . . ) is the i-th axial distance (mm) counted fromthe object side, and Ni (i=1,2,3, . . . ) and vi (i=1,2,3, . . . ) arethe refractive index (Nd) and the Abbe number (vd), to the d-line, ofthe i-th optical element counted from the object side. In theconstruction data, as the axial distances that vary during zooming,values in the shortest focal length condition (wide-angle limit, W), inthe middle focal length condition (middle, M) and in the longest focallength condition (telephoto limit, T) are shown. The overall focallengths (f, mm) and the f-numbers (FNO) in the focal length conditions(W), (M) and (T) are shown together with other data.

The surfaces whose radii of curvature ri are marked with asterisks areaspherical, and are defined by the following expression (AS) expressingthe aspherical surface configuration. Aspherical data of the embodimentsis shown as well.

$\begin{matrix}{x = {\frac{C_{0}y^{2}}{1 + \sqrt{1 - {ɛ\; C_{0}^{2}y^{2}}}} + {\sum{{Ai}\mspace{14mu} y^{i}}}}} & ({AS})\end{matrix}$where,

-   -   x represents the shape (mm) of the aspherical surface (i.e., the        displacement along the optical axis at the heighty in a        direction perpendicular to the optical axis of the aspherical        surface),    -   Co represents the curvature (mm⁻¹) of the reference aspherical        surface of the aspherical surface,    -   y represents the height in a direction perpendicular to the        optical axis,    -   ε represents the quadric surface parameter, and    -   Ai represents the aspherical coefficient of order i.

EXAMPLE 1

f = 5.1-8.9-14.7 Fno. = 2.16-3.04-4.10 [Radius of [Axial [Refractive[Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 17.931  d1 = 1.000 N1 = 1.82302 ν1 = 36.21 r2 = 10.890  d2 =  3.800 r3 = ∞  d3 =12.400 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500-3.379-1.696 r5* =−436.249  d5 =  1.000 N3 = 1.65461 ν3 = 46.54 r6* = 5.978  d6 =  1.270r7 = 10.014  d7 =  1.656 N4 = 1.84666 ν4 = 23.82 r8 = 33.402  d8 =11.535-4.725-1.020 r9 = ∞  d9 =  0.600 r10 = 6.649 d10 =  6.427 N5 =1.75450 ν5 = 51.57 r11 = −7.769 d11 =  1.000 N6 = 1.84666 ν6 = 23.82r12* = 30.896 d12 =  2.020-8.365-14.584 r13* = −21.319 d13 =  3.778 N7 =1.52510 ν7 = 56.38 r14 = −5.800 d14 =  2.804-1.390-0.560 r15 = −11.316d15 =  0.800 N8 = 1.48749 ν8 = 70.44 r16 = −32.669 d16 =  0.100 r17 = ∞d17 =  2.000 N9 = 1.51680 ν2 = 64.20 r18 = ∞[Aspherical Coefficient]r5*ε=0.10000000D+01A4=0.95247363D−05A6=0.44499878D−05A8=0.20201509D−06A10=0.15630434D−08r6*ε=0.10000000D+01A4=−0.44138182D−03A6=−0.17905680D−04A8=−0.12106726D−06A10=0.25333947D−07r13*ε=0.10000000D+01A4=0.11420046D−02A6=0.61304067D−04A8=−0.24678605D−05A10=0.38078980D−06r14*ε=0.10000000D+01A4=−0.17175253D−02A6=0.35415900D−04A8=−0.51967472D−05A10=0.10804669D−06

EXAMPLE 2

f = 5.1-8.9-14.7 Fno. = 2.16-2.97-4.10 [Radius of [Axial [Refractive[Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1* = 77.048  d1 = 1.000 N1 = 1.66602 ν1 = 30.12 r2 = 10.412  d2 =  3.701 r3 = ∞  d3 =12.400 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  0.200 r5 = 12.063  d5 = 1.645 N3 = 1.84898 ν3 = 33.15 r6 = 22.797  d6 =  2.045-5.298-3.490 r7*= 74.513  d7 =  1.000 N4 = 1.52510 ν4 = 56.38 r8* = 6.297  d8 =  1.041r9 = 7.766  d9 =  1.464 N5 = 1.79850 ν5 = 22.6  r10 = 10.311 d10 =13.841-5.438-1.000 r11 = ∞ d11 =  0.600 r12 = 6.616 d12 =  5.892 N6 =1.75450 ν6 = 51.57 r13 = −10.215 d13 =  1.000 N7 = 1.84666 ν7 = 23.82r14* = 18.124 d14 =  2.079-8.055-15.451 r15* = −23.464 d15 =  3.400 N8 =1.52510 ν8 = 56.82 r16 = −6.333 d16 =  2.476-1.650-0.500 r17 = 14.316d17 =  1.000 N9 = 1.84833 ν9 = 29.89 r18 = 10.360 d18 =  0.907 r19 = ∞d19 =  2.000 N10 = 1.51680  ν10 = 64.20  r20 = ∞[Aspherical Coefficient]r1*ε=0.10000000E30 01A4=0.63638407E31 04A6=0.36516691E−06A8=0.15861666E−08r7*ε=0.10000000E+01A4=0.63173747E−03A6=042880271E−04A8=−0.13655536E−05A10=0.17341485E−07r8*ε=0.10000000E+01A4=−0.78352207E−03A6=0.45124782E−04A8=−0.17639048E−05A10=0.22553499E−07r15*ε=0.10000000E+01A4=0.10864595E−02A6=0.63616957E−04A8=−0.36734216E−05A10=0.41688467E−06

r16*ε=0.10000000E+01A4=0.14356439E−02A6=0.25426605E−04A8=−0.32121190E−05A10=0.95302924E−07

EXAMPLE 3

f = 4.5-7.9-12.9 Fno. = 2.1-2.8-3.7 [Radius of [Axial [Refractive [AbbeCurvature] Distance] Index(Nd)] Number(νd)] r1 = 4101.218  d1 =  0.700N1 = 1.78589 ν1 = 44.20 r2 = 19.552  d2 =  0.900 r3 = ∞  d3 =  8.000 N2= 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.000-3.596-1.000 r5* = 56.521  d5 = 0.800 N3 = 1.57501 ν3 = 41.49 r6* = 4.357  d6 =  1.021 r7 = 7.895  d7 = 1.6000 N4 = 1.84666 ν4 = 23.82 r8 = 21.921  d8 = 10.752-3.530-0.969 r9= ∞  d9 =  0.650 r10 = 5.274 d10 =  4.755 N5 = 1.75450 ν5 = 51.57 r11 =−9.977 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12 = −9.977 d12 =  0.800 N7= 1.84666 ν7 = 23.82 r13* = 15.094 d13 =  2.179-7.261-12.815 r14* =−25.000 d14 =  3.200 N8 = 1.52510 ν8 = 56.38 r15* = −5.767 d15 = 1.453-0.996-0.600 r16 = 10.099 d16 =  0.983 N9 = 1.70055 ν9 = 30.11 r17= 6.767 d17 =  0.948 r18 = ∞ d18 =  1.500 N10 = 1.51680  ν10 = 64.20 r19 = ∞[Aspherical Coefficient]r5*ε=0.10000000E+01A4=−0.44053024E−03A6=−0.45582866E−04A8=0.56807258E−05A10=−0.21748168E−06r6*ε=0.10000000E+01A4=−0.19077667E−02A6=−0.45431102E−04A8=−0.17609821E−05A10=−0.26911785E−08r13*ε=0.10000000E+01A4=0.24256912E−02A6=0.13113475E−03A8=−0.19935678E−05A10=0.20427432E−05r14*ε=0.10000000E+01A4=−0.76241384E−03A6=−0.45684352E−04A8=0.74367662E−05A10=0.17395830E−06r15*ε=0.10000000E+01A4=0.16617833E−02A6=−0.97370809E−04A8=0.83998804E−05

EXAMPLE 4

f = 4.5-7.6-12.9 Fno. = 2.1-2.8-2.97 [Radius of [Axial [Refractive [AbbeCurvature] Distance] Index(Nd)] Number(νd)] r1 = −25.000  d1 =  0.800 N1= 1.63980 ν1 = 34.55 r2 = −115.843  d2 =  0.100 r3 = ∞  d3 =  9.200 N2 =1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.000-4.551-2.772 r5* = 21.359  d5 = 0.800 N3 = 1.83400 ν3 = 37.15 r6* = 5.824  d6 =  3.352 r7 = 14.337  d7=  1.500 N4 = 1.84666 ν4 = 23.82 r8 = 52.503  d8 = 12.765-4.785-0.910 r9= ∞  d9 =  0.700 r10 = 12.888 d10 =  2.200 N5 = 1.75450 ν5 = 51.57 r11 =−36.914 d11 =  0.100 r12 = 4.598 d12 =  3.800 N6 = 1.48749 ν6 = 70.44r13 = 181.628 d13 =  0.010 N7 = 1.51400 ν7 = 42.83 r13 = 181.628 d14 = 1.000 N8 = 1.84666 ν8 = 23.82 r15* = 3.955 d15 =  1.500-6.298-12.506r16* = 10.062 d16 =  2.000 N9 = 1.48749 ν9 = 70.44 r17* = −8.840 d17 = 1.472-1.104-0.600 r18 = ∞ d18 =  1.700 N10 = 1.51680  ν10 = 64.20  r19= ∞[Aspherical Coefficient]r5*ε=0.10000000E+01A4=0.28920160E−03A6=−0.24770223E−04A8=0.40226114E−06r6*ε=0.10000000 E+01A4=−0.28416506E−03A6=−0.39127534E−04A8=0.10049102E−06r15*ε=0.10000000E+01A4=0.22971891E−02A6=0.61362182E−04A8=0.3054044E−04r16*ε=0.10000000 E+01A4=0.29657551E−02A6=−0.32988137E−03A=0.18146796E−04r17*ε=0.10000000E+01A4=0.65616586E−02A6=−0.68518707E−03A=0.33543925E−04

EXAMPLE 5

f = 4.5-7.9-12.9 Fno. = 2.1-2.89-3.8 [Radius of [Axial [RefractiveCurvature] Distance] Index(Nd)] [Abbe Number(νd)] r1 = 16.688  d1 = 0.800 N1 = 1.54072 ν1 = 47.22 r2 = 7.343  d2 =  2.500 r3 = ∞  d3 = 8.400 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500-2.971-1.500 r5* =164.473  d5 =  0.800 N3 = 1.62004 ν3 = 36.26 r6* = 4.995  d6 =  1.353 r7= 10.132  d7 =  2.267 N4 = 1.84666 ν4 = 23.82 r8 = 69.912  d8 =11.101-4.724-0.862 r9 = ∞  d9 =  0.650 r10 = 5.681 d10 =  5.504 N5 =1.75450 ν5 = 51.57 r11 = −10.007 d11 =  0.010 N6 = 1.51400 ν6 = 42.83r12 = −10.007 d12 =  0.800 N7 = 1.84666 ν7 = 23.82 r13* = 13.518 d13 = 1.987-8.774-14.499 r14* = 72.616 d14 =  3.700 N8 = 1.52510 ν8 = 56.38r15* = −8.793 d15 =  3.078-1.197-0.806 r16 = ∞ d16 =  1.500 N9 = 1.51680ν9 = 64.20[Aspherical Coefficient]r5*ε=0.10000000E+01A4=−0.50212557E−03A6=0.58262738E−04A8=−0.45960476E−05A10=0.10745067E−06r6*ε=0.10000000E+01A4=−0.17341477E−02A6=0.76117570E−04A8=−0.99234139E−05A10=0.25780579E−06r13*ε=0.10000000 E+01A4=0.22365769E−02A6=0.79579971E−04A8=0.53500363E−05A10=0.10651891E−05r14*ε=0.10000000E+01A4=−0.74920577E−03A6=−0.44003627E−04A8=−0.46232075E−05A10=0.52351697E−06r15*ε=0.10000000E+01A4=0.27419718E−03A6=−0.15545535E−03A8=0.68734468E−03

EXAMPLE 6

f = 4.5-7.9-12.9 Fno. = 2.1-2.86-3.78 [Radius of [Axial [RefractiveCurvature] Distance] Index(Nd)] [Abbe Number(νd)] r1 = 131.891  d1 = 0.800 N1 = 1.51742 ν1 = 52.41 r2 = 11.659  d2 =  1.650 r3 = ∞  d3 = 8.000 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500 r5* = 35.321  d5 = 0.800 N3 = 1.52200 ν3 = 52.20 r6* = 4.893  d6 =  1.276 r7 = 7.568  d7 = 2.000 N4 = 1.84666 ν4 = 23.82 r8 = 12.453  d8 = 11.029-3.671-0.998 r9 =∞  d9 =  0.6500 r10 = 5.991 d10 =  4.909 N5 = 1.75450 ν5 = 51.57 r11 =−9.320 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12 = −9.320 d12 =  1.400 N7= 1.84666 ν7 = 23.82 r13* = 26.705 d13 =  1.370-6.910-12.832 r14* =−16.667 d14 =  3.678 N8 = 1.52510 ν8 = 56.38 r15* = −6.042 d15 = 4.129-3.385-2.697 r16 = ∞ d16 =  1.500 N9 = 1.51680 ν9 = 64.20 r17 = ∞[Aspherical Coefficient]

r5*ε=0.10000000E+01A4=0.43313297E−03A6=−0.10070798E−03A8=0.84126830E−05A10=−0.26384097E−06

r6*ε=0.10000000E+01A4=−0.30789841E−03A6=−0.11170196E−03A8=0.66705245E−05A10=−0.24941305E−06r13*ε=0.10000000 E+01A4=0.15633769E−02A6=0.51050129E−04A8=0.24266581E−06A10=0.67988002E−06r14*ε=0.10000000E+01A4=−0.12218564E−02A6=0.25134426E−03A8=−0.53931767E−04A10=0.43794302E−05r15*ε=0.10000000E+01A4=0.94953834E−03A6=−0.27258786E−04A8=0.28920117E−05

EXAMPLE 7

f = 4.5-7.9-12.9 Fno. = 2.0-2.85-3.74 [Radius of [Axial [Refractive[Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 33.725  d1 = 0.800 N1 = 1.85000 ν1 = 40.04 r2 = 11.351  d2 =  1.200 r3 = 25.554  d3=  1.458 N2 = 1.75450 ν2 = 51.57 r4 = 37.693  d4 =  0.800 r5 = ∞  d5 = 8.200 N3 = 1.84666 ν3 = 23.82 r6 = ∞  d6 =  1.500-3.420-1.500 r7 =97.822  d7 =  0.800 N4 = 1.52510 ν4 = 56.38 r8* = 5.111  d8 =  0.743 r9= 6.467  d9 =  2.000 N5 = 1.84666 ν5 = 23.82 r10 = 10.975 d10 =10.550-4.249-1.028 r11 = ∞ d11 =  0.650 r12 = 6.194 d12 =  5.604 N6 =1.75450 ν6 = 51.57 r13 = −6.781 d13 =  0.010 N7 = 1.51400 ν7 = 42.83 r14= −6.781 d14 =  1.183 N8 = 1.84666 ν8 = 23.82 r15* = 38.043 d15 = 3.186-8.555-13.974 r16* = −16.667 d16 =  3.812 N9 = 1.77250 ν9 = 49.77r17* = −5.893 d17 =  2.712-1.724-1.447 r18 = ∞ d18 =  1.500 N10 =1.51680  ν10 = 64.20  r19 = ∞[Aspherical Coefficient]r8*ε=0.10000000E+01A4=−0.15428275E−03A6=−0.42877249E−04A8=0.15793970E−06A10=−0.20720675E−07r10*ε=0.10000000E+01A4=−0.64995991E−04A6=0.17099407E−04A8=−0.16152162E−07r15*ε=0.10000000E+01A4=0.13775987E−02A6=0.47166979E−04A8=0.20857832E−05A10=0.23955123E−06r16*ε=0.10000000E+01A4=−0.20963217E−02A6=0.74122201E−04A8=−0.11877575E−04A10=0.53768544E−06r17*ε=0.10000000E+01A4=0.80770597E−04A6=0.42148914E−05A8=0.60309537E−07

EXAMPLE 8

f = 4.5-7.9-12.9 Fno. = 2.0-2.81-3.67 [Radius of [Axial [Refractive[Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 15.797  d1 = 0.800 N1 = 1.58913 ν1 = 61.11 r2 = 7.557  d2 =  2.700 r3 = ∞  d3 = 8.009 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500-3.160-1.500 r5 =−26.368  d5 =  0.800 N3 = 1.48749 ν3 = 70.44 r6* = 4.708  d6 =  0.518 r7= 5.361  d7 =  2.154 N4 = 1.85000 ν4 = 40.04 r8* = 10.802  d8 =11.235-4.910-1.331 r9 = ∞  d9 =  0.650 r10 = 6.699 d10 =  4.000 N5 =1.75450 ν5 = 51.57 r11 = −9.744 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12= −9.744 d12 =  0.800 N7 = 1.79850 ν7 = 22.60 r13 = 67.530 d13 =  0.537r14 = 28.497 d14 =  0.800 N8 = 1.58340 ν8 = 30.23 r15* = 18.947 d15 = 2.612-8.560-14.167 r16* = −30.752 d16 =  4.200 N9 = 1.52510 ν9 = 56.38r17* = −5.241] d17 =  2.934-1.651-1.283 r18 = ∞ d18 =  1.500 N10 =1.51680  ν10 = 64.20  r19 = ∞[Aspherical Coefficient]r6*ε=0.10000000E+01A4=−0.10145481E−02A6=0.72075706E−04A8=0.19174089E−05A10=−0.46087898E−07r8*ε=0.10000000E+01A4=0.70130028E−03A6=0.46972417E−04A8=0.33943302E−05r15*ε=0.10000000E+01A4=0.14752106E−02A6=0.55770047E−04A8=−0.10845300E−05A10=0 0.44294001E−06r16*ε=0.10000000E+01A4=−0.18942226E−02A6=0.69566995E−04A8=−0.13206893E−04A10=0.73140343E−06r17*ε=0.10000000E+01A4=0.74167453E−03A6=−0.16789975E−04A8=0.14074200E−05

EXAMPLE 9

f = 4.5-7.9-12.9 Fno. = 2.0-2.88-3.77 [Radius of [Axial [Refractive[Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 24.847  d1 = 0.800 N1 = 1.85026 ν1 = 32.15 r2 = 9.507  d2 =  1.200 r3* = 18.529  d3=  1.878 N2 = 1.52200 ν2 = 52.20 r4 = 37.877  d4 =  0.800 r5 = ∞  d5 = 8.200 N3 = 1.84666 ν3 = 23.82 r6 = ∞  d6 =  1.500-3.255-1.500 r7 =−23.840  d7 =  0.800 N4 = 1.52200 ν4 = 52.20 r8* = 5.612  d8 =  0.500r9* = 6.897  d9 =  2.300 N5 = 1.84666 ν5 = 23.82 r10* = 17.332 d10 =11.012-4.659-1.072 r11 = ∞ d11 =  0.650 r12 = 6.160 d12 =  6.000 N6 =1.75450 ν6 = 51.57 r13 = −6.615 d13 =  0.010 N7 = 1.51400 ν7 = 42.83 r14= −6.615 d14 =  0.969 N8 = 1.84666 ν8 = 23.82 r15* = 29.536 d15 = 1.496-7.489-12.982 r16* = −31.130 d16 =  4.200 N9 = 1.52510 ν9 = 56.38r17* = −5.934 d17 =  3.226-1.831-1.680 r18 = ∞ d18 =  1.500 N10 =1.51680  ν10 = 64.20  r19 = ∞[Aspherical Coefficient]r3*ε=0.10000000E+01A4=0.11455958E−03A6=−0.33371789E−06A8=0.16291474E−07r8*ε=0.10000000E+01A4=0.11930738E−03A6=−0.41125994E−04A8=0.93638465E−06A9=−0.22174114E−07r10*ε=0.10000000E+01A4=−0.62127445E−04A6=0.14433401E−04A8=−0.23787289E−06r15*ε=0.10000000E+01A4=0.15502859E−02A6=0.47738830E−04A8=0.42055482E−05A10=0.17243267E−06r16*ε=0.10000000E+01A4=−0.17058224E−02A6=0.76334079E−04A8=−0.14552475E−04A10=0.69411194E−06r17*ε=0.10000000E+01A4=0.88231293E−04A6=−0.18063594E−04A8=0.70394395E−06

EXAMPLE 10

f = 4.5-7.9-12.9 Fno. = 2.0-2.69-3.45 [Radius of [Axial [Refractive[Abbe Curvature] Distance] Index(Nd)] Number(νd)] r1 = 29.225  d1 = 0.800 N1 = 1.58913 ν1 = 61.11 r2 = 9.824  d2 =  2.288 r3 = ∞  d3 = 8.000 N2 = 1.84666 ν2 = 23.82 r4 = ∞  d4 =  1.500-4.764-1.500 r5 =37.705  d5 =  0.800 N3 = 1.48749 ν3 = 70.44 r6* = 4.423  d6 =  0.500 r7= 5.513  d7 =  2.00 N4 = 1.85000 ν4 = 40.04 r8* = 8.515  d8 =12.201-3.853-1.149 r9 = ∞  d9 =  0.650 r10 = 6.604 d10 =  4.885 N5 =1.75450 ν5 = 51.57 r11 = −7.480 d11 =  0.010 N6 = 1.51400 ν6 = 42.83 r12= −7.480 d12 =  0.800 N7 = 1.79850 ν7 = 22.60 r13 = −19.278 d13 = 0.900-1.200-1.501 r14 = −7.554 d14 =  0.800 N8 = 1.58340 ν8 = 30.23r15* = 153.332 d15 =  2.658-7.442-13.108 r16* = 7.127 d16 =  4.046 N9 =1.52510 ν9 = 56.38 r17* = −66.811 d17 =  1.000 r18 = ∞ d18 =  1.500 N10= 1.51680  ν10 = 64.20  r19 = ∞[Aspherical Coefficient]r6*ε=0.10000000E+01A4=−0.13188674E−03A6=−0.11077449E−03A8=0.36905376E−05A10=0.29138999E−06r8*ε=0.10000000E+01A4=−0.72069648E−04A6=0.45751204E−04A8=0.72652405E−06r15*ε=0.10000000E+01A4=0.15958174E−02A6=−0.11349576E−04A8=0.19068718E−04A10=0.94307372E−06r16*ε=0.10000000E+01A4=−0.20231807E−03A6=0.92943008E−04A8=−0.39179305E−05A10=0.15776897E−06r17*ε=0.10000000E+01A4=0.11215385E−02A6=0.29269875E−04A8=0.12347517E−04

FIGS. 11A to 11I through 20A to 20I which are graphic representations ofaberrations of the first to the tenth examples show aberrations of thezoom lens systems of the examples in in-focus state at infinity. Inthese figures, (W), (M) and (T) show aberrations (from the left,spherical aberration, sine condition, astigmatism and distortion; Y′(mm)is the maximum image height [corresponding to the distance from theoptical axis] on the image sensor) in the shortest focal lengthcondition, in the middle focal length condition and in the longest focallength condition, respectively. In the graphic representations ofspherical aberration, the solid line (d) shows spherical aberration tothe d-line, the chain line (g) shows spherical aberration to the g-line,the chain double-dashed line (c) shows spherical aberration to thec-line, and the broken line (SC) shows sine condition. In the graphicrepresentations of astigmatism, the broken line (DM) shows astigmatismon the meridional image plane, and the solid line (DS) shows astigmatismon the sagittal image plane. In the graphic representations ofdistortion, the solid line shows distortion % to the d-line.

As described above, according to the zoom lens systems of theembodiments, an imaging device can be provided that is compact althoughhaving a high-performance and high-magnification zoom lens system.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodification depart from the scope of the present invention, they shouldbe construed as being included therein.

1. An imaging device comprising: a zoom lens system having a pluralityof lens units and forming an optical image of an object so as tocontinuously optically zoom by varying distances between all of theplurality of lens units; the zoom lens system including from an objectside: a first lens unit being overall negative and including areflecting surface that bends a luminous flux substantially 90 degrees;and a second lens unit disposed with a variable air distance from thefirst lens unit and having a negative optical power, the second lensunit being disposed next to the first lens unit; and an image sensorconverting the optical image formed by the zoom lens system to anelectric signal, wherein the zoom lens system fulfills the followingcondition:1.5<|f12w |fw<4 where f12w is the composite focal length of the firstlens unit and the second lens unit in the shortest focal lengthcondition and fw is the overall focal length of the zoom lens system inthe shortest focal length condition.
 2. An imaging device as claimed inclaim 1, wherein the first lens unit includes a right-angle prism havingan internal reflecting surface as the reflecting surface.
 3. An imagingdevice as claimed in claim 2, wherein the following condition issatisfied:Np ≧1.55 where Np is a refractive index to a d-line of the right-angleprism.
 4. An imaging device as claimed in claim 1, the zoom lens systemfurther comprises, a third lens unit disposed with a variable airdistance from the second lens unit, and having a positive optical power,a fourth lens unit disposed with a variable air distance from the thirdlens unit, and having a positive optical power.
 5. An imaging device asclaimed in claim 4, wherein the zoom lens system consists of said firstthrough fourth lens units.
 6. An imaging device as claimed in claim 4,the zoom lens system further comprising: a fifth lens unit disposed witha variable air distance from the fourth lens unit.
 7. An imaging deviceas claimed in claim 1, wherein, the first lens unit is fixed withrespect to the image plane in zooming from the shortest focal lengthcondition to the longest focal length condition.
 8. An imaging device asclaimed in claim 1, wherein, the second lens unit moves so as to draw alocus of a U-turn convex to the image side in zooming from the shortestfocal length condition to the longest focal length condition.
 9. Animaging device as claimed in claim 1, wherein the zoom lens system hasnot more than two lens elements disposed on the object side of thereflecting surface.
 10. An imaging device as claimed in claim 9, whereinthe zoom lens system has only one lens element disposed on the objectside of the reflecting surface.
 11. An imaging device as claimed inclaim 1, wherein the zoom lens system fulfills the following condition:0.5<|f1/f2 |<5 where f1 is the focal length of the first lens unit andf2 is the focal length of the second lens unit.
 12. An imaging devicecomprising: a zoom lens system having a plurality of lens units andforming an optical image of an object so as to continuously opticallyzoom by varying distances between all of the plurality of lens units;the zoom lens system including from an object side: a first lens unitbeing overall negative and including a reflecting surface that bends aluminous flux substantially 90 degrees; a second lens unit disposed witha variable air distance from the first lens unit and having a negativeoptical power, the second lens unit being disposed next to the firstlens unit; and a third lens unit disposed with a variable air distancefrom the second lens unit and having a positive optical power; and animage sensor converting the optical image formed by the zoom lens systemto an electric signal, wherein the zoom lens system fulfills thefollowing condition:0.4<|f12w|/f3<1.5 where f12w is the composite focal length of the firstlens unit and the second lens unit in the shortest focal lengthcondition and f3 is the focal length of the third lens unit.
 13. Animaging device as claimed in claim 1, wherein the zoom lens systemfulfills the following condition:1.0 <D/fw <2.6 where D represents an axial distance between a surface atthe most object side surface of the first lens unit and the reflectionsurface; and fw represents a focal length of the entire zoom lens systemin a wide angle condition.
 14. A camera comprising: an imaging deviceincluding: a zoom lens system having a plurality of lens units andforming an optical image of an object so as to continuously opticallyzoom by varying distances between all of the plurality of lens units,the zoom lens system having from an object side: a first lens unit beingoverall negative and including a reflecting surface that bends aluminous flux substantially 90 degrees; and a second lens unit disposedwith a variable air distance from the first lens unit and having anegative optical power, the second lens unit being disposed next to thefirst lens unit; and an image sensor converting the optical image formedby the zoom lens system to an electric signal, wherein the zoom lenssystem fulfills the following condition:1.5<|f12w |/fw<4 where f12 w is the composite focal length of the firstlens unit and the second lens unit in the shortest focal lengthcondition and fw is the overall focal length of the zoom lens system inthe shortest focal length condition.
 15. A camera as claimed in claim14, wherein the first lens unit includes a right-angle prism having aninternal reflecting surface as the reflecting surface.
 16. A camera asclaimed in claim 14, the zoom lens system further comprises, a thirdlens unit disposed with a variable air distance from the second lensunit, and having a positive optical power, a fourth lens unit disposedwith a variable air distance from the third lens unit, and having apositive optical power.
 17. A camera as claimed in claim 14, wherein,the first lens unit is fixed with respect to the image plane in zoomingfrom the shortest focal length condition to the longest focal lengthcondition.
 18. A camera as claimed in claim 14, wherein, the second lensunit moves so as to draw a locus of a U-turn convex to the image side inzooming from the shortest focal length condition to the longest focallength condition.
 19. A camera as claimed in claim 14, wherein the zoomlens system has not more than two lens elements disposed on the objectside of the reflecting surface.
 20. A camera as claimed in claim 14,wherein the zoom lens system fulfills the following condition:0.5<|f1/f2|<5 where f1 is the focal length of the first lens unit and f2is the focal length of the second lens unit.
 21. A camera comprising: animaging device including: a zoom lens system having a plurality of lensunits and forming an optical image of an object so as to continuouslyoptically zoom by varying distances between all of the plurality of lensunits, the zoom lens system having from an object side: a first lensunit being overall negative and including a reflecting surface thatbends a luminous flux substantially 90 degrees; a second lens unitdisposed with a variable air distance from the first lens unit andhaving a negative optical power, the second lens unit being disposednext to the first lens unit; and a third lens unit disposed with avariable air distance from the second lens unit and having a positiveoptical power; and an image sensor converting the optical image formedby the zoom lens system to an electric signal, wherein the zoom lenssystem fulfills the following condition:0.4<|f12w |/f3<1.5 where f12w is the composite focal length of the firstlens unit and the second lens unit in the shortest focal lengthcondition and f3 is the focal length of the third lens unit.
 22. Acamera as claimed in claim 14, wherein the zoom lens system fulfills thefollowing condition:1.0<D/fw <2.6 where D represents an axial distance between a surface atthe most object side surface of the first lens unit and the reflectionsurface; and fw represents a focal length of the entire zoom lens systemin a wide angle condition.
 23. An imaging device as claimed in claim 1,further comprising a third lens unit disposed with a variable airdistance from the second lens unit and having a negative optical power,wherein the zoom lens system fulfills the following condition:0.4<f12w|/f3<1.5 where f3 is the focal length of the third lens unit.24. A camera as claimed in claim 14, wherein the zoom lens systemfurther comprises a third lens unit disposed with a variable airdistance from the second lens unit and having a positive optical power,wherein the zoom lens system fulfills the following condition:0.4<|f12w|/f3<1.5 where f3 is the focal length of the third lens unit.